In recent years, technology known as OpenFlow has been proposed (see Non-Patent Literature 1 and 2). In OpenFlow, communication is taken as end-to-end flow, and path control, failure recovery, load balancing, and optimization are performed on a per-flow basis. An OpenFlow switch as specified in Non-Patent Literature 2 is provided with a secure channel for communication with an OpenFlow controller, and operates according to a flow table in which addition or rewriting is instructed as appropriate by the OpenFlow controller. In the flow table, for each flow there are definitions of sets of match conditions (Match Fields) for collation with packet headers, flow statistical information (Counters), and instructions (Instructions) that define processing content (see “5.2 Flow Table” in Non-Patent Literature 2).
For example, when an OpenFlow switch receives a packet, a search is made for an entry having a match condition (see “5.3 Matching” in Non-Patent Literature 2) that matches header information of the received packet, from the flow table. As a result of the search, in a case where an entry matching the received packet is found, the OpenFlow switch updates the flow statistical information (Counters) and also implements processing content (packet transmission from a specified port, flooding, dropping, and the like) described in an Instructions field of the entry in question, for the received packet. On the other hand, as a result of the search, in a case where an entry matching the received packet is not found, the OpenFlow switch transmits a request for entry configuration to the OpenFlow controller via the secure channel, that is, a request for transmission of control information for processing the received packet. The OpenFlow switch receives a flow entry with processing content determined and updates the flow table. In this way, the OpenFlow switch performs packet forwarding using entries stored in the flow table as control information.
Patent Literature 1 discloses a configuration where, in a communication system using the abovementioned OpenFlow, an OpenFlow controller generates and transmits an encapsulated packet in which a flow entry for recording and a normal packet are related, and flow entries can be collectively recorded in an OpenFlow switch on a particular path.
Patent Literature 2 discloses a configuration where, in a communication system using the abovementioned OpenFlow, when a plurality of service-providing servers that provide a service to a client terminal issue a load balancing request to an OpenFlow controller, the OpenFlow controller changes flow entry (entries) configured in the switch.